In a wireless communication system, there may be multi-RAT user equipment (UE) with capability for access to two or more radio access technologies (RATs). In order to access specific RAT, connection is established to specific RAT and data is transmitted and received based on UE request.
However, even if the multi-RAT UE has capability of accessing two or more RATs, the multi-RAT UE cannot simultaneously access multiple RATs. That is, currently, even if a UE has multi-RAT capability, the UE cannot simultaneously transmit and receive data through different RATs.
Such conventional multi-RAT technology does not require interworking between a wireless LAN and a cellular network, there is a problem in terms of overall low system efficiency. In addition, research has not been conducted to overcome the problem.